Latched type shunted contact for three stage contact construction



NOV- 8, 1950 A. s. CASWELL ETAL 2,959,654

LATCHED TYPE SHUNTED CONTACT FOR THREE STAGE CONTACT CONSTRUCTION 5Sheets-Sheet 1 Filed Dec. 19, 1958 Nov. 8,y 1960 A. s. cAswELL ETAT2,959,654

LATCHED TYPE SHUNTED CONTACT FOR THREE STAGE CONTACT CONSTRUCTION 3Sheets-Sheet. 2

Filed Dec. 19, 1958 Nov. 8, 1960 A. s. CASWELL ErAL 2,959,654

LATCEED TYPE SHUNTED CONTACT FOR THREE sTACE CONTACT CONSTRUCTION FiledDeo. 19, 1958 5 Sheets-Sheet 5 lHllWlllll /a United States Patent2,959,654 Patented Nov. s, 1960 hice LATCHED TYPE SHUNTED CONTACT FORTHREE STAGE CONTACT CONSTRUCTION Arthur S. Caswell, Greensburg, andWilliam A. Carter, Chester, Pa., assignors to I-T-E Circuit BreakerCompany, Philadelphia, Pa., a corporation of Pennsyl- Vania Filed Dec.19, 1958, Sel'. No. 781,541

7 Claims. (Cl. 200-146) The instant invention generally =relates tocircuit breakers and more particularly to a circuit breaker in which themagnetic blowout means -is mechanically inserted in the circuit by anovel latched type shunt contact.

Air magnetic circuitbreakers are usually provided with an arcextinguishing means including a plurality of spaced arc plates stackedso as to form an arc chute, and associated with the chute is a blowoutcoil which is positioned so as to direct the arc formed by the partingof the circuit breaker contacts into the arc chute. In one prior artconstruction, the blowout coil was mechanically inserted into thecircuit by the main arcing contacts. However, on the closing of thebreaker the blowout coil was not protected from the high magnetic forcesaccompanying high peak inrush currents when closing on a fault current.In order to protect the blowout coil from these high magnetic forces onclosing :of the circuit breaker, other prior art constructions haveprovided an arc transfer means in the form of a jump gap. This hasresulted in poor interruption at low values of current since the arc isoften unable to jump the gap thereby preventing the arcing current fromflowing through the blowout coil.

In the circuit breaker of the instant invention the movable contactbridge has been provided with a contact assembly including a maincontact, a shunt contact, and an arcing contact which cooperate withco-rresponding stationary contacts. The bridge contacts are so mountedthat upon closing ofthe circuit breaker the shunt contacts are first toclose, followed by the arcing contacts, and finally the main contactswhereas upon opening, the main contacts are first to open, followed bythe shunt contacts, and finally the arcing contacts.

The shunt contacts are positioned in the circuit such that when they areclosed the blowout coil is completely shorted. Thus, upon closing of thecircuit breaker the initial formation of a continuous current pathresults in the shorting of the blowout coil thereby protecting this coilfrom peak inrush currents. The shunt contacts also provide additionalprotection for the main contacts on opening of the breaker. Y

The preceding operation is accomplished by mounting the shunt contact tothe circuit breaker bridge in a manner such that it is always biasedtoward engagement with its stationary cooperating shunt contact. A shuntcontact latch is also carried by the bridge and is biased towardlatching position. When the bridge moves the contacts toward circuitclosed position, the engagement of the movable shunt contact with itscooperating stationary shunt contact moves the shunt contact, againstits bias, to a position wherein the shunt contact is beyond the engagedposition of the latch and is maintained in this position with the forceof the biasing means.

On the opening of the circuit breaker, the latch engages and is held inengagement with the shunt contact until such time as the bridge reachesthe end of the opening stroke. At this time, the latch strikes `a tripplate thereby releasing the shunt contact so that it is free to be actedupon by its bias. With the shunt contact unlatched upon closing ofthe'circuit breaker, the shunt contact is the first of the three movablecontacts to engage its cooperating stationary contact.

The advantage of this construction over its conventional counterparts inthe prior art is that the high peak inrush currents, encountered whenclosing Ia circuit breaker on a faulted circuit are diverted from theblowoutcoil by the shunt contact. In this manner, the extra highmagnetic force, which varies as the square of the current, that theblowout coils must be built to withstand, is greatly reduced. Inaddition, a greater protection for the main contacts is provided.

Accordingly, a primary object of the instant invention is to provide anovel construction for a circuit breaker wherein the blowout coilsthereof are mechanically inserted into the circuit.

Another object is to provide a circuit breaker having a latched typeshunt contact for protecting the blowout coils upon closing of thecircuit breaker.

Still another object is to provide a circuit breaker wherein the movablebridge thereof is provided with three contacts whose closing and openingsequences are different from one another.

A further object is to provide a shunt contact for the protection of acircuit breaker blowout coil and a latch means engageable with the shuntcontact whereby the shunt contact is latched while the circuit breakeris being opened and remains unlatched while the circuit breaker is beingclosed.

These `as well as other objects of the instant invention shall becomereadily apparent after reading the following description of theaccompanying drawings in which:

Figures 1-4 are side elevations of the contact structure illustratingthe positions of the contacts at different positions of the contactbridge. In Figure l the circuit breaker is fully closed; in Figure 2 thecircuit breaker is fully open with the shunt contact unlatched; inFigure 3 the shunt contacts and arcing contacts are engaged during theclosing stroke and the main contacts are still open; and the shuntcontacts are not latched, while in Figure 4 the shunt contacts and thearcing contacts are engaged during the opening stroke with the shuntcontacts being latched and the main contacts being open.

Figures 5 and 6 are schematics of a circuit breaker constructed inaccordance with the instant invention. In Figure 5 the circuit breakeris shown during the closing operation and in Figure 6 the circuitbreaker is shown during the opening operation.

Now referring to the figures and more particularly to Figures 5 and 6,circuit breaker 20 comprises a stationary contact structure includingcontacts 21, 23, 25 and a movable contact structure including contacts22, 24, 26. Cooperating contacts 21, 22 are designated the maincontacts, cooperating contacts 23, 24 are designated the arcingcontacts, and cooperating contacts 25, 26 are designated the shuntcontacts.

Movable contact structure 24, 26, 28 is mounted to one end of conductingbridge 27 while the other end of bridge 27 is pivoted at 28 to lowercurrent stud 29. Stationary main contact 2l and shunt contact 25 areboth mounted to upper current stud 30. The stationary arcing contact 23is mounted to arcing contact member 34 which is insulated from uppercurrent stud 3i) by insulating member 96 interposed between member 99and upper current stud 30. An insulating sleeve 98 disposed in anaperture through member 99 surrounds the body of screw 97 which securesmember 99 to upward extension 9S of upper stud 30. Insulating washer 97'is interposed between the head of screw 97 and member 99. Current studs29, 30 extend through inthereof to arcing contactmem'ber 34. Therear=runner` 36 of parallel' plate arc chute 37 is also electricallyconnected to arcing contactY member 34 while front runner 38 iselectrically connected to lower current stud 29. As -is well known inthe art, blowout coil 35 is positioned to force an electric current arcdrawn bei tween arcing contacts 23,' 24, upon parting thereof, into arcchute 37 where the arcing gases are cooled and otherwise de-ionized tovbring about the extinctionv of the arc.

As will b'e more fully explained hereinafter, as bridge 27 is movedclockwise about pivot 25 from the circuit breaker closed position(Figure l) by any one of many operating mechanisms known to the art, themain contacts 2l, 22 are first to part. Since lthey are parallel byshunt contacts 25, 26, no arcing will occur at main contacts 2l, 22.Therefore, shunt contacts 25, 26 part so that blowout coil 35 isenergized even before arcing contacts 23, 24 pant. Thus, thev arc, fromits inception, is acted upon by the magnetic force accompanying currentflow through blowout coil 35. Since the energization of blowout coil 35is independent of arc current magnitude even an arc of low current valuewill be acted upon by some magnetic force urging the arc into arc chute37.

Upon counter-clockwise movement of bridge 27 from the circuit breakerfull open position (Figure 2), shunt contacts 25, 25 will be rst toengage to complete a current path between the upper 3) and the lower 29current studs which bypasses blowout coil 35. Thus, coil 35 is protectedfrom high inrush currents encountered when closing circuit breaker on afaulted circuit. After shunt vcontacts 25, 26 are closed, arcingcontacts 23, 24 will close followed by the closing of main contacts 21,22. The Structure for achieving the contact opening and closing sequencehereinbeforel outlined will now be described with particular referenceto Figures 1 4.

Movable shunt contact 26 is mounted to movable contact element 4o nearthe lower end thereof while movable arcing contact 24 is mounted nearthe upper end of element 4t).l Contact element 40 is pivotally mountednear arcing contact 24 to pivot 41 which is secured to bridge 27 nearthe free end thereof.

Compression spring 42 seated between clip 43 and con`` tact element 40biases element 4i) clockwise about pivot 4i. Clip comprises a U-shapedmember whose free ends are bent over pins 44, 45 to secure clip 43 tobridgel 27. Spring 42'sur'rounds rod 46 which is pivoted at one end 47to contact element 4t) near shunt contact 26. The other end 43 of rod 46is threaded and extends through an opening in the web of clip 43 to beengaged by knob 49 which establishes the point in the closing stroke ofbridge 27 at which shunt contacts 25, 26 are initially engaged. n p

An L-shaped latch member 50 is pivotally mounted at pin 51 to bridge 27.Oneend of latch member 50 is secured to one end of tension spring'52whose other end is secured -to trip lever 53 near the pin 54 about whichlever 53 is pivoted. Pin 54 is mounted to triangular extension 55 ofbridge 27.

Spring 52 biases latch member 50 clockwise about lpin 5l to a latchingposition wherein latch tip 56 is operatively positioned to engage latchsurface 57 of contact element 40. The cooperation of latch tip 56 andlatch surface 57 prevents contact element 40 from being moved clockwiseunder the Vinlluence of spring 42 to the limit established by knob 49.Lever 53 yis also biased by spring 52 to a ylatching position or aposition at which lever 53 does not prevent latch member 50 fromassuming its latching position. One end 58 of trip lever 53 isengageable with Atrip `plate 59 at the end of the -bridge opening stroke(Figure 2). The engagement of lever end 58 with plate 59 moves triplever 53 clockwise about pivot 54 against the influence of spring 52.Thls causes the other end 60 of lever 53 to engage latch member 50 andmove it counter-clockwise to an unlatching pos1t1on thereby permittingmovable shunt contact 26, under the urging of spring 42, to move tolimit established by knob 49.

Beginning with the circuit breaker 20 in the fully closed position ofFigure 1, the initial movement of bridge 27 on the clockwise openingstroke causes main contacts 2l, 22 ,to separate. During this movement ofbridge 27, spring 42 moves element 40 clockwise since latch surface 57is spaced from latch tip 56 so that during this period shunt contacts25, 26 remain in engagement. Also, during this period, spring 61, whichis interposed between abutment 62 and nut 63, urges rod l64 to the rightwith respect tov Figure'l. Abutments 62 and 67 extend upward from thesupport member 99 for arcing contact 23. Since rod kv64 is pivotallyconnected at 65 to arcing contact member 34,y this member will berotated clockwise about pivot 66, mounted to member 99, so that arcingcontacts 23, 24 remain engaged. At this point, it should be understoodthat even lthough contact 23 Vhas been referred toas a stationarycontact it is actually a semi-stationary contact. v

Continued clockwise movement'ofY bridge 27 causes latch tip 56 4toengage latch surface 57 thereby preventing further clockwise movement ofelement 40. Thus, movable shunt contact 26 now moves together withbridge 27 and disengages stationary shunt contact 25. However, duringthis interval member 34 continues clockwise movement about pivot 66 sothat arcing contacts 23, 24 remain in engagement.

Arcing contacts 23, 24 remain engaged until nut 63 engages abutment 67through which rod 64 extends. Continued movement of bridge 27 thencauses the separation of arcing contacts 25, 26.

When the bridge 27 finally reaches the end of the opening stroke (Figure2), lever end 58 engages trip plate 59 causing latch member 50 to' bemoved to an unlatching position. Spring 42 then urges latch surface 57past latch tip 56 so that movable arcing contact 26 is moved to the leftto an extended position.

Since movable shunt contact 26 is now extended, the counter-clockwiseclosing stroke movement of bridge 27 first causes shunt contacts 25, 26to be brought into engagement. Arcing contact 23 is now in its extendedposition so that arcing contacts 23, `24 are next to engage. Finally atthe end of the closing stroke main contacts v21, 22 are brought intoengagement.

During the portion of the closing stroke after engagement of shuntcontacts 25, 26 element 43 is forced counterclockwise against the -forceof spring 42. This causes latch surface 57 to move past latch tip 56 sothat tip 56 may once Yagain assume a latching position in preparationfor thesubsequent opening stroke.

Thus, this invention provides a novel circuit breaker constructionwhereby the blowout coils are mechanically inserted into theY circuityet protected from high peak inrush currents. This is achieved byproviding a pair of latchable shunt contacts in addition to theconventional arcing and main contacts. The operation of the contacts aredifferently sequenced on the opening and closing strokes of the circuitbreaker that is, on closing the order of contact engagement is shuntcontacts rst to engage, followed by the engagement of the arcingcontacts, and lastly the engagement of the main contacts. On-

opening the main contacts are first to part, followed by the parting ofthe shunt contacts, and lastly the arcing contacts part.

Although we have here described preferred `embodiment :of our novelinvention, many variations and'modi-v cations willnow be apparent tothose skilled Yin the specific disclosure herein, but only by theappending claims.

We claim:

1. A circuit breaker comprising a first, a second, and a third pair ofcooperating contacts; a first means operable between a first and asecond position; one contact of each of said pairs of cooperatingcontacts being mounted to said first means; each of said pairs ofcooperating contacts being operated into engagement by operation of saidfirst means to said first position and being operated out of engagementby operation of said first means to said second position; upon operationof said first means from said first to said second position said firstpair of contacts is first to disengage, followed by the disengagement ofsaid second pair of contacts, and finally followed by the disengagementof said third pair of contacts; upon operation of said first means fromsaid second to said first position said second pair of contacts is firstto engage, followed by the engagement of said third pair of contacts,and finally followed by the engagement of said first pair of contacts.

2. A circuit breaker comprising a first, a second, and a third pair ofcooperating contacts; a first means operable between a first and asecond position; one contact of each of said pairs of cooperatingcontacts being mounted to said first means; each of said pairs ofcooperating contacts being operated into engagement by operation of saidfirst means to said first position and being operated out of engagementby operation of said first means to said second position; upon operationof said first means from said first to said second position said firstpair of contacts is first to disengage, followed by the disengagement ofsaid second pair of contacts, and finally followed by the disengagementof said third pair of contacts; upon operation of said first means fromsaid second to said first position said second pair of contacts is firstto engage, followed by the engagement of said third pair of contacts,and finally followed by the engagement of said first pair of contacts;said circuit breaker including an arc extinguishing means comp-rising anarc chute and a blowout coil operatively positioned to urge an electriccurrent arc, initiated by the disengagement of said third set ofcontacts, deeply into said arc`A chute; said arc chute including a firstand a second arc runner and a stack of spaced plates positioned betweensaid arc runners; said blowout coil being electrically connected betweenthe other contact of said second pair of contacts and said first runner.

3. A circuit breaker comprising a first, ia second, and a third pair ofcooperating contacts; a first means operable between a first and asecond position; one contact of each of said pairs of cooperatingcontacts being mounted to said first means; each of said pairs ofcooperating contacts being operated into engagement by operation of saidfirst means to said first position and being operated out of engagementby operation of said first means to said second position; upon operationof said first means from said first to said second position said firstpair of contacts is first to disengage, followed by the disengagement ofsaid second pair of contacts, and finally followed by the disengagementof said third pair of contacts; upon operation of said first means fromsaid second to said first position said second pair of contacts is firstto engage, followed by the engagement of said third pair of contacts,and finally followed by the engagement of said first pair of contacts;said circuit breaker including an arc extinguishing means comprising anarc chute and a blowout coil operatively positioned to urge an electriccurrent arc, initiated by the disengagement of said third set ofcontacts, deeply into said arc chute; said arc chute including a firstand a second arc runner and a stack of spaced plates positioned betweensaid arc runners; said blowout coil being electrically connected betweenthe other contact of said second pair of contacts and said first runner;the other contact of lsaid third pair of contacts being electricallyconnected to said first runner.

4. A circuit breaker comprising a first, a second, and a third pair ofcooperating contacts; a first means operable between a first and asecond position; one contact of each of said pairs of cooperatingcontacts being mounted to said first means; each of said pairs ofcooperating contacts being operated into engagement by operation of saidfirst means to said first position and being operated out of engagementby operation of said first means to said second position; upon operationof said first means from said first to said second position said firstpair of contacts is first to disengage, followed by the disengagement ofsaid second pair of contacts, and finally followed by the disengagementof said third pair of contacts; upon operation of said first means fromsaid second to said first position said second pair of contacts is firstto engage, followed by the engagement of said third pair of contacts,and finally followed by thel engagement of said first pair of contacts;said circuit breaker including an arc extinguishing means comprising anarc chute and a blowout coil operatively positioned to urge an electriccurrent arc, initiated by the disengagement of said third set ofcontacts, deeply into said arc chute; said arc chute including a firstand a second arc runner and a stack of spaced plates positioned betweensaid arc runners; said blowout coil being electrically connected betweenthe other contact of said second pair of contacts and said first runner;the other contact of said third pair of contacts being electricallyconnected to said first runner; a first biasing means urging said onecontact of said second pair of contacts in a first direction towardengagement with its cooperating contact; a latch means carried by saidfirst means and engageable with said one contact of said second pair ofcontacts after said first set of contacts are disengaged upon operationof said first means from said first to said second position; said latchmeans when engaged with said one contact of said second pair of contactsrestraining this contact from movement in said first direction.

5. A circuit breaker comprising a first, a second, and a third pair ofcooperating contacts; a first means operable between a first and asecond position; one contact of each of said pairs of cooperatingcontacts being mounted to said first means; each of said pairs ofcooperating contacts being operated into engagement by operation of saidfirst means to said first position and being operated out of engagementby operation of said first means to said second position; upon operationof said first means from said first to said second position said firstpair of contacts is first to disengage, followed by the disengagement ofsaid second pair of contacts, and finally followed by the disengagementof said third pair of contacts; upon operation of said first means fromsaid second to said first position said second pair of contacts is firstto engage, followed by the engagement of said third pair of contacts,and finally followed by the engagement of said first pair of contacts;said circuit breaker including an are extinguishing means comprising anarc chute and a blowout coil operatively positioned to urge an electriccurrent arc, initiated by the disengagement of said third set ofcontacts, deeply into said are chute; said arc chute including a firstand a second arc runner and a stack of spaced plates positioned betweensaid arc runners; said blowout coil being electrically connected betweenthe other contact of said second pair of contacts and said first runner;the other contact of said third pair of contacts being electricallyconnected to said first runner; a first biasing means urging said onecontact of said second pair of contacts in a first direction towardengagement With its cooperating contact; a latch means carried by saidfirst means and engageable with said one contact of said second pair ofcontacts after said first set of contacts are disengaged upon operationof said first means fronrsaid first Ato said second position;"saidlatchfmeans when Vengagedk with said' one contact of said second pair ofcontacts restraining thiscontkact 'from movement in said firstdirection; said latch'meansengageable with said one contact of saidsecond pair of contacts prior to the disengagement of said third pair ofcontacts as said first means is operated from said first tosaid secondposition.

6. A circuit breaker comprising a first, a second, and a third pair ofcooperating contacts; a first means operable between a firstand a secondposition; one contac of each of said pairs of cooperating contacts beingmounted to saidfirst means; each of saiddpairs' of col-l operatingcontacts being operated into Iengagement by operation of said firstmeans to said first position and being operated out of engagement byoperation of said first means to said secondposition; upon operation ofsaid firstmeans fromsaid first to said second'position said first pairof contactsis first to disengage; followed1 by the disengagementof said'secondpair of contacts, and finally followed bythe disengagement ofnsaidthird pair of contacts; upon operation of `said first means' from saidsecond toV said first position said second pair of' contacts is firstto'engageLfollowed by the engagement of said` third pair ofk contacts, andfinally followed by the engagement of said first pair of contacts;said'circuit breaker including an arc extinguishing means conrprising anarc chute and a blowout coil operatively positioned to urge an electriccurrentarc, initiated by the disengagement of said third setoff/contacts; deeply into said arc chute; said arc chute includingafirst and a second arc runner and a stack of spaced plates positionedbetween said arc runners; said blowout vcoil being electricallyconnected between theothe'r` Contact, of said second pair of contactsand said first runner; the other Contact of said third pair of contactsbeing electrically connected to said first runner; a first biasing meansurgi ing said one contact of said second pair of contacts in a firstdirection toward engagement with its cooperating contact; a latch meanscarried by'said first means and engageable with said one contact of saidsecondpair of contacts after said first set'of contacts are disengageduponoperation of said first means `from said first to said secondposition; said latch means when engaged with said one contact ofsaid'second pair of contacts restrain-l ing this contact from movementkin said first direction; said latch means engageable with said onecontact of said ysecond pair of contacts prior to the disengagement ofsaid third pair of contacts as said first means lis op? erated from saidfirst to said second position; trip means actuated when said first meansis in Ysaid second position; said trip means when actuated operatingsaid latch means to release said one contact of said second set ofcontacts thereby enabling this contact to be moved in said firstdirection through the action of said first biasing means.

7. A circuit lbreaker comprisinga first,l a second, and a third pair ofcooperating contacts; a first means oper; able between a first and asecond position; one contact of each of said pairs of4cooperatingicontactsbeing mounted to said first means; each of saidpairs of cooperatingy contacts being operated into engagement byloperation of said first means to -said first position and beingoperated out of engagement by operation of said first means to saidsecond position; upon operation of saidl first means from said first tosaid second position said first pair of contacts is first to disengage,followed by the disengagement of said second pair of contacts,` andfinally followed by the disengagement of said third pair of contacts;upon operation of said first means from said second to Asaid firstposition said second pair of contacts is first to engage, followed bythe engagement of said third pair of contacts, and finally followed bythe engagement of said first pair of contacts; said circuit breakerincluding an arcpextinguishing means comprising an arc chute and ablowout coil operatively positioned to urgean electric current arc,initiated by the disengagement of said third set of contacts, deeplyinto said arc chute; said arc chute including a first and a second arcrnnner and a stack of spaced plates positioned between said arc runners;said blowoutcoil being electrically connected between the other contactof said' second pair of contacts and said first runner; the othercontact of said third pair of contacts beingelectrically connected tosaid first runner; a first biasing means urgingsaid one contact of saidsecond pair of contacts in a first direction toward engagement with itscooperating contact; a latch means carried by said first means andengageable with said one contact ofsaid second pair of contacts aftersaid first set of contacts are disengaged upon operation of said firstmeans from said first to said rsecond position; said latch means whene11- gaged with said one contact of said second pair of contactsrestraining this contact from movement in said first direction; saidlatch means engageable with said one contact of said second pair ofcontacts prior to the disengagement of saidthird pair of contactsrassaid first means is operated from said first to said second position;trip means actuated when said first means is in said second position;said trip means when actuated operating said latch means to release saidone `contact of said second set of contacts thereby enabling thiscontact to'be moved in said first direction through the actionrof saidfirst biasing means; a second biasing means urging the other contact ofsaid third set of contacts ina second direction toward engagement withits cooperating contact.

References VCited in the file of this patent UNITED STATES PATENTS

